Systems and methods for cooling computer data centers

ABSTRACT

A data center cooling system is provided to maintain data center temperatures without introducing detrimental conditions into the data center. The computer data center cooling system has a cooling tower that controllably provides cooling water at a temperature in a particular range. The cooling water is then pumped through a series of filtration, treatment, monitoring and separation subsystems to reliably clean the cooling water of particles and treat the cooling water to reduce the harmful effects of corrosion and scaling. Further control subsystems utilize PID loop controllers to maintain the temperature to the air-handler unit cooling coils to within one (1) degree Fahrenheit of a set point that is determined by the computer data center air conditions. The cooling system utilizes either a primary loop or a combination of primary/secondary loops to achieve the highest system efficiency.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

This invention relates to cooling systems that provide cooling tocomputer data centers.

2. Background and Relevant Art

Generally, modern computer data centers have servers, switches, andnetworking equipment that are maintained to environmental standards,such as those discussed in ASHRAE TC 9.9, which is hereby incorporatedby reference in its entirety. Data centers use a significant amount ofenergy to operate, and in fact, data center energy use is one of thefastest growing segments of energy consumption in the United States.Experts predict that by the year 2020, data center energy use willsurpass the metals industry as the largest segment of energy consumptionin the United States. This fact is driving data centers, especiallylarge data centers, to find and use more energy efficient methods andsystems.

One way in which data centers may become more energy efficient isthrough increasing the efficiency of the cooling systems used to coolthe data center. Conventional cooling systems may include a chiller,direct expansion gas cooling, water-side economizer, air-sideeconomizer, or some combination of these components. In addition,conventional cooling systems often utilize water or glycol as a coolingmedium in closed loop systems. Alternatively, conventional coolingsystems may utilize computer room air cooling (CRAC) units placed nearthe server racks in a data center. In these systems, cooling isaccomplished by direct expansion, water-side economizer, or chilledwater.

Conventional cooling systems typically use between 0.5 and 1.8 kilowattsper ton of cooling produced. As an example, a conventional largecollocation facility may use 400 tons of cooling, and therefore, a datacenter cooling system that decreases this load would significantlyreduce overall energy costs.

Efforts directed at energy efficient cooling systems have focused onefficient air or other fluid distribution. For example, there have beeninventions directed towards increasing the efficiency of chillers (USPub. 20030067745), air distribution (US Pub. 20090168345, US Publ.20040206101, U.S. Pat. No. 7,112,131, U.S. Pat. No. 6,859,366), hot andcold aisle isolation (US Pub. 20080185446), using outside air (US Pub.20090210096), and even locating data centers on barges and usingseawater to cool them (US Pub. 20080209234).

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention include systems, devices andmethods used to increase the energy efficiency of data center coolingsystems. In particular, example embodiments of the present inventioninclude an indirect open-loop evaporative cooling system that providescooling to data centers. By using a unique open-loop system, higherenergy efficiencies are obtained because the system cooling water isexposed to ambient air with a low wet bulb temperature. This exposureallows the cooling water to utilize the energy transfer involved invaporization to cool the cooling water to within approximately three tofive degrees Fahrenheit of the dew point. The system therefore, uses thedry ambient air as the ultimate thermal sink of the system.

In this way, embodiments of the present invention can provide coolingsystems that produce cooled water at an energy cost ranging fromapproximately 0.05 to 0.15 kilowatts per ton. At this rate, in a 400-tonconventional large collocation facility, the energy savings would bebetween approximately 2 and 6 gigawatt hours per year.

Example embodiments of the present invention are advantageous becausethey provide a significant increase in the operating efficiency comparedto conventional data center cooling systems. For example, the use of anopen-loop system gains efficiencies in power consumption and waterusage. The electrical power is saved through the increases in coolingefficiency, and water consumption is reduced by the elimination of theneed to reject large amounts of heat generated by mechanical coolingdevices, such as chillers.

In a preferred configuration of the invention, an open-loop coolingsystem that provides cooling water of a desired cooling temperature isused for cooling environmentally sensitive volumes of air. This systemincludes an evaporative heat exchanger. Within the evaporative heatexchanger, cooling water is cooled by mixing the cooling water with airthat has a low wet bulb temperature.

Also, the system includes a temperature control subsystem which isconnected to the evaporative heat exchanger and controls the temperatureof the cooling water circulating in the open-loop cooling system. Thetemperature control subsystem includes a temperature monitor thatmeasures the temperature of the cooling water. The subsystem alsoincludes a mechanical cooler that provides supplementary mechanicalcooling to the cooling water when the temperature control subsystemindicates the temperature of the cooling water is hotter than thedesired cooling temperature. The subsystem also includes a mixingelement that heats the cooling water if the temperature controlsubsystem indicates the temperature of the cooling water is cooler thanthe desired cooling temperature.

The open-loop cooling system also includes at least one air-handlerunit, which is connected to the evaporative heat exchanger and thetemperature control subsystem. The air-handler unit facilitates thetransfer of heat from the environmentally sensitive volume of air to thecooling water.

According to another configuration of the invention, an open-loopcooling system used in cooling a data center includes at least oneair-handler unit. The air-handler unit is configured to facilitate thetransfer of heat from air in the data center to cooling water thatcirculates through a cooling water system. The cooling water systemprovides cooling water at a desired cooling temperature.

The cooling water system includes a cooling tower, which is connected tothe air-handler unit. Within the cooling tower, the cooling water mixeswith air that has a low wet bulb temperature. The mixing cools thecooling water.

The cooling water system also includes a temperature control subsystem,which is connected to the cooling tower and the air-handler unit. Thetemperature control subsystem controls the temperature of the coolingwater circulating in the cooling water system. The subsystem includes atemperature monitor that measures the temperature of the cooling water.The subsystem also includes a mechanical cooler that providessupplementary mechanical cooling to the cooling water if the temperaturecontrol subsystem indicates the temperature of the cooling water ishotter than the desired cooling temperature. The subsystem also includesa mixing element that heats the cooling water if the temperature controlsubsystem indicates the temperature of the cooling water is cooler thanthe desired cooling temperature.

The invention extends to a method for data center cooling using anopen-loop evaporative system that facilitates the production of coolingwater at a desired cooling temperature. The method includes the step ofmixing heated cooling water with air that has a low wet bulb temperaturein a cooling tower. This step utilizes the latent heat of vaporizationto cool the cooling water. The cooling water circulates through one ormore cooling coils of an air-handler unit. Within the air-handler unit,the air from the data center is forced across the cooling coil such thatthe air transfers its heat to the cooling water. This step heats thecooling water, which returns to the evaporative cooling tower.

Additional features and advantages of embodiments of the presentinvention will be set forth in the description that follows, and in partwill be obvious from the description, or may be learned by the practiceof such exemplary embodiments. The features and advantages of suchembodiments may be realized and obtained by means of the instruments andcombinations particularly pointed out in the appended claims. These andother features will become more fully apparent from the followingdescription and appended claims, or may be learned by the practice ofsuch exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 illustrates a block diagram of an example of the data centercooling system;

FIG. 2 illustrates a piping diagram of an example of the data centercooling system;

FIG. 3 illustrates a psychometric chart showing the cooling process thatcan be accomplished by embodiments of the cooling system;

FIG. 4 illustrates an embodiment of the air-handler unit;

FIG. 5 illustrates air entrapment remedies used in an embodiment of thecooling system; and

FIG. 6 illustrates a system that may be used for freeze protection instandby pumps.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention include systems, devices andmethods used to increase the energy efficiency of data center coolingsystems, e.g., computer data centers. In particular, example embodimentsof the present invention include an indirect open-loop evaporativecooling system that provides cooling to data centers. By using a uniqueopen-loop system, higher energy efficiencies are obtained because thesystem cooling water is exposed to ambient air with a low wet bulbtemperature. This exposure allows the cooling water to utilize theenergy transfer involved in vaporization to cool the cooling water towithin approximately three to five degrees Fahrenheit of the dew point.The system therefore, uses the dry ambient air as the ultimate thermalsink of the system.

As an overview, FIG. 1 shows an example of an open-loop cooling system50 according to one embodiment of the present invention. For example,FIG. 1 illustrates that the open-loop cooling system 50 can include acooling tower 100, one or more tower pumps 101, one or more system pumps106, a filtration subsystem 102, a chemical treatment and monitoringsubsystem 103, a temperature control subsystem 104, one or moreair-handler units 105, a computer data center 140, data center air 145,and cooling water 55 that circulates through the open-loop coolingsystem 50.

Generally, the open-loop cooling system 50 can include piping sectionsthrough which the cooling water 55 circulates and which connectcomponents making up the open-loop cooling system 50. For example, inthe embodiment illustrated in FIG. 1, the cooling water 55 circulatesthrough a cooling tower outlet piping section 116, a tower pump inletpiping section 117, a tower pump outlet piping section 136, a chemicaltreatment inlet piping section 118, a chemical treatment outlet pipingsection 119, a filter inlet piping section 120, a filter outlet pipingsection 121, a mechanical cooling inlet piping section 122, a mechanicalcooling outlet piping section 123, a mixing element inlet piping section128, a mixing element outlet piping section 129, a mixing elementcross-over piping section 130, a system pump inlet piping section 131, asystem pump outlet piping section 132, an air-handler inlet pipingsection 133, and a system return piping section 135. In alternateembodiments, the configuration of the piping sections as well as theinclusion of various sections may vary from one embodiment to the nextdepending the cooling requirements of the data center 140.

Notwithstanding the various piping sections configurations, FIG. 1illustrates that the open-loop cooling system 50 includes cooling tower100. In one example embodiment, cooling tower 100 has a high efficiencycounter-flow design with an induced draft fan. In alternate embodiments,the cooling tower may utilize other designs and configurations thatperform the same or similar function as will be described below.

In particular, the cooling tower 100 uses the induced draft fan to drawor blow atmospheric air 51 through an atmospheric air inlet 107. Theatmospheric air 51 interacts with the cooling water 55 that exits thesystem return piping section 135 and enters the cooling tower 100. Asthe cooling water 55 exiting the return piping section 135 mixes withthe atmospheric air 51, the latent heat of vaporization is absorbed fromthe cooling water 55 and the atmospheric air 51. As a result, thecooling water 55 is cooled.

The rate and amount of cooling performed within the cooling tower 100may depend on the wet bulb characteristics of the atmospheric air 51.Generally, the lower the wet bulb temperature of the atmospheric air 51,the more cooling that takes place within the cooling tower 100. Thus,the open-loop cooling system 50 can be installed in geographic locationsknown to have atmospheric air 51 with low wet bulb temperatures, such asdeserts or arid climates. In these optimal climates, the cooling tower100, may cool the cooling water 55 to within three to five degreesFahrenheit of the dew point. Aside from the optimal climates, theopen-loop cooling system 50 can be installed in a wide-range ofgeographic locations, although the exact efficiencies of the open-loopcooling system 50 may vary with atmospheric characteristics.

Returning to the open-loop cooling system 50, after the atmospheric air51 is cooled within the cooling tower 100, the atmospheric air 51 isexhausted to the atmosphere through an atmospheric air exhaust 110. Forexample, FIG. 1 illustrates that the cooling tower 100 includes anatmospheric air exhaust 110. In one example embodiment, the atmosphericair exhaust 110 is located opposite of the atmospheric air inlet 107 toform a defined flow path of the atmospheric air 51 through the coolingtower 100. In alternate embodiments, the location of the atmospheric airexhaust 110 can vary.

Just as the atmospheric air 51 exhausts from the cooling tower 100, thecooling water 55 which has been cooled also exits the cooling tower 100.In one example embodiment, the cooling tower 100 is connected to thetower pumps 101 via the tower outlet piping section 116. In particular,after the cooling water 55 is cooled within the cooling tower 100, thecooling water 55 accumulates within the cooling tower 100 and the towerpumps 101 pump the cooling water 55 through the tower outlet pipingsection 116, into the tower pump inlet piping section 117, and throughthe tower pumps 101.

Although one or more tower pumps 101 can be employed in variousconfigurations, FIG. 2 illustrates one example embodiment in which thetower pumps 101 a and 101 b are configured in parallel. In the parallelconfiguration, one of tower pumps is designated as the operating towerpump 101 a, while the other tower pump is designated as the standbytower pump 101 b. Thus, the operating tower pump 101 a normally pumpsthe cooling water 55, while the standby tower pump 101 b remains instandby in case the operating tower pump 101 a fails or another systemcondition requires the use of the standby tower pump 101 b. In alternateembodiments, the tower pumps 101 may be configured in series or a singlepump may be utilized.

The tower pumps 101 are used to circulate the cooling water 55 throughvarious components and subsystems of the open-loop cooling system 50. Inone example embodiment, the tower pumps 101 are connected to thechemical treatment and monitoring subsystem 103 and the filtrationsubsystem 102 via the tower pump outlet piping section 136. Inparticular, the tower pump outlet piping section 136 can connect to thechemical treatment inlet piping section 118 to circulate water throughthe chemical treatment and monitoring subsystem 103. The chemicaltreatment outlet piping section 119 is configured to return coolingwater 55 that has been chemically treated to the tower pump outletpiping section 136.

In one embodiment of the open loop cooling system 50, at least a portionof the cooling water 55 may be routed through the chemical treatment andmonitoring subsystem 103. For example, in the configuration illustratedin FIG. 1, a portion of the cooling water 55 exiting the tower pumps 101into the tower pump outlet piping section 136 enters the chemicaltreatment and monitoring subsystem 103 via the chemical treatment inletpiping section 118. The remainder of the cooling water 55 exiting thetower pumps 101 remains in the tower pump outlet piping section 136 andproceeds to the filter inlet piping section 120. In alternativeembodiments, none or all of the cooling water 55 exiting the tower pumps101 may enter the chemical treatment and monitoring subsystem 103.

The portion of cooling water that enters the chemical treatment andmonitoring subsystem 103 can be controlled by one or more valves. Thevalves can be electronically controlled and coupled with other devices,such as flow rate meters, to direct substantially exact portions of thecooling water 55 to the chemical treatment and monitoring subsystem 103in order to maintain consistent chemical properties in the cooling water55.

Additionally, a dedicated chemical subsystem pump may circulate theportion of cooling water 55 that enters the chemical treatment andmonitoring subsystem 103. For example in the embodiment illustrated inFIG. 2, a dedicated chemical subsystem pump 210 circulates the coolingwater 55 through the chemical treatment and monitoring subsystem 103. Inalternate embodiments, the open-loop cooling system 50 may utilize analternate pressure source to circulate the cooling water 55 through thechemical treatment and monitoring subsystem 103.

In addition to the various components used to direct cooling water 55 tothe chemical treatment and monitoring subsystem 103, the chemicaltreatment and monitoring subsystem 103 can include various components tochemically monitor the cooling water 55 and chemically treat the coolingwater 55. For example, FIG. 2 illustrates that the chemical treatmentand monitoring subsystem 103 can include a corrosion coupon rack 202. Inoperation, the corrosion coupon rack 202 includes coupons of knownsize/weight of a material that can corrode when exposed to the coolingwater 55, such as copper. In alternative embodiments, other corrodiblematerials can be used within the corrosion coupon rack 202.

The coupons are positioned on the corrosion coupon rack 202 such thatthe coupons interface with the cooling water 55. The rate at which thecoupons corrode depends upon the corrosive properties of the coolingwater 55. The coupons can then be removed from the corrosion coupon rack202 and measured and/or weighed to determine and monitor the corrosiveproperties of the cooling water 55. For example, if the cooling water 55becomes too corrosive, remedial actions can be taken, such as addingadditional chemicals to the cooling water 55 to make the cooling water55 less corrosive.

In one example embodiment, the chemical treatment and monitoringsubsystem 103 includes a chemical injection pump 204, as illustrated inFIG. 2. The chemical injection pump 204 allows an operator to injectchemicals as required into the open-loop cooling system 50 via thechemical treatment and monitoring subsystem 103. In one example, anoperator can control the chemical injection pump 204 from a controlcenter. In alternate embodiments, the chemical treatment and monitoringsubsystem 103 automatically injects chemicals as required by theopen-loop cooling system 50.

In addition to the chemical injection pump 204, the chemical treatmentand monitoring subsystem 103 may include additional components. Forexample, FIG. 2 illustrates an embodiment of the chemical treatment andmonitoring subsystem 103 that includes a centrifuge 203. The centrifuge203 can separate particulate matter contained in the cooling water 55that is routed to the chemical treatment and monitoring subsystem 103.In alternate embodiments, the chemical treatment and monitoringsubsystem 103 can include similar components and processes that separatecorrosive particular matter from the cooling water 55.

In addition to the components described above, the chemical treatmentand monitoring subsystem 103 can include a wide array of chemicalmonitoring equipment used to monitor a wide array of chemical propertiesof the cooling water 55, depending on the desired chemical properties ofthe cooling water 55. For example, in one embodiment, the cooling water55 is substantially pure water. In alternative embodiments, however, thecooling water 55 can be chemically treated water, a water-based chemicalsolution, or another cooling medium with carefully engineeredthermodynamic properties.

Once the cooling water 55 or a portion of cooling water 55 is processedthrough the chemical treatment and monitoring subsystem 103, the coolingwater 55 can enter the filtration subsystem 102. For example, as shownin FIG. 1, the chemical treatment and monitoring subsystem 103 isconnected to the filtration subsystem 102 via the chemical treatmentoutlet piping section 119, and the filter inlet piping section 120. Thecooling water 55 exiting the chemical treatment and monitoring subsystem103 via the chemical treatment outlet piping section 119 mixes with thecooling water 55 that did not enter the chemical treatment andmonitoring subsystem 103 in the filter inlet piping section 120, andthen enters the filtration subsystem 102. In alternative embodiments,the cooling water 55 exiting the chemical treatment and monitoringsubsystem 103 via the chemical treatment outlet piping section 119 maymix with the cooling water 55 that did not enter the chemical treatmentand monitoring subsystem 103 at another point in the open-loop coolingsystem 50.

The filtration subsystem 102 filters the cooling water 55 before itenters the filter outlet piping section 121. The filtration subsystem102 can include, but is not limited to media filters, screen filters,disk filters, slow sand filter beds, rapid sand filters and clothfilters that can be configured to various sizes of particles from thecooling water 55. In at least one embodiment, the filtration subsystem102 substantially prevents a particle of a predetermined size or largerfrom circulating with the cooling water 55 through the portion of theopen-loop cooling system 50 behind the filtration subsystem 102.

Once the cooling water 55 passes through the filtration subsystem 102,the cooling water 55 can enter one or more subsystems within theopen-loop cooling system 50. For example, as shown in FIG. 1, thefiltration subsystem 102 is connected to the temperature controlsubsystem 104 via the filter outlet piping section 121. In alternateembodiments, the connection between the filtration subsystem 102 and thetemperature control subsystem 104 can exist in an alternate location inthe open-loop cooling system 50.

Generally, the temperature control subsystem 104 provides the coolingwater 55 with supplementary temperature control in the event that thecooling tower 100 was unable to produce cooling water 55 with a desiredtemperature for the cooling cycle. For example, in the event that theatmospheric air 51 becomes humid, the atmospheric air 51 will have ahigher wet bulb temperature. This condition reduces the efficiency ofthe cooling that occurs in the cooling tower 100 and may necessitatesupplementary mechanical cooling in the temperature control subsystem104.

Additionally, the temperature control subsystem 104 can be configured tofunction only if the cooling water 55 is not at the desired temperature.For example, if the cooling water 55 is at the desired temperature, thecooling water 55 can bypass the temperature control subsystem 104.

Depending on the temperature of the cooling water 55 entering thetemperature control subsystem 104, the temperature control subsystem 104can employ various components to adjust the temperature of the coolingwater 55. In one example embodiment, the temperature control subsystem104 can include a mechanical cooler 137, such as a chiller, that canprovide supplementary mechanical cooling to the cooling water 55 asrequired to produce cooling water 55 with the desired temperature forthe cooling cycle.

Thus, the combination of the cooling tower 100 (high efficient cooling)and the mechanical cooler 137 (lower efficient cooling) used to controlthe temperature of the cooling water 55 is highly energy efficient andmay allow temperature control of the cooling water 55 to within one (1)degree Fahrenheit. For example, under certain conditions, theatmospheric air 51 has wet bulb temperature properties that allow thecooling tower 100 to adequately cool the cooling water 55, thusproviding the highest efficiency possible as no supplementary mechanicalcooling is needed. With other conditions, for example when theatmospheric air 51 has a higher wet bulb temperature, the cooling water55 can require supplementary mechanical cooling. However, because thecooling tower 100 has provided most of the cooling, the mechanicalcooler 137 only needs to lower the temperature of the cooling water 55 afew degrees. Thus, the majority of the work performed in the open loopcooling system 50 is provided by the high efficient cooling componentwhile the lower efficient cooling is only utilized as required and in alimited fashion. Therefore, the temperature of the cooling water 55 iscontrolled in a highly energy efficient manner.

In addition, FIG. 1 illustrates that the temperature control subsystem104 can be configured in series with the cooling tower 100. Configuringthe temperature control subsystem 104 in series with the cooling tower100 eliminates the need for an additional cooling tower, heatexchangers, or secondary closed loop for chilled water or glycol, aswith conventional systems.

As shown in FIG. 1, the mechanical cooler 137 is connected to the filteroutlet piping section 121 via the mechanical cooling inlet pipingsection 122 and the mechanical cooling outlet piping section 123. Acontrolled portion of the cooling water 55 exiting the filtrationsubsystem 102 through the filter outlet piping section 121 enters themechanical cooling inlet piping section 122. The remainder of thecooling water 55 remains in the filter outlet piping section 121.Depending on the wet bulb temperature of the data center air 145, theamount of cooling water 55 that enters the mechanical cooler 137 canrange from none of the cooling water 55 to all of the cooling water 55.

In alternative embodiments, the portion of the cooling water 55 enteringthe mechanical cooler 137 could be based on other physical conditions inthe open-loop cooling system 50. For example, the portion of the coolingwater that enters the mechanical cooler 137 from the filter outletpiping section 121 may be controlled such that condensation does notform in the air-handler units 105.

In addition, in the embodiment illustrated in FIG. 1, the cooling water55 that entered the mechanical cooler 137 via the mechanical coolinginlet piping section 122 is cooled in the mechanical cooler 137 thenexits the mechanical cooler 137 via the mechanical cooling outlet pipingsection 123. The cooling water 55 exiting the mechanical cooler 137 viathe mechanical cooling outlet piping section 123 mixes with the portionof the cooling water 55 that exited the filtration subsystem 102 via thefilter outlet piping section 121. The result of the mixing of thecooling water 55 exiting the mechanical cooler 137 via the mechanicalcooling outlet piping section 123 with the cooling water 55 exiting thefiltration subsystem 102 via the filter outlet piping section 121 is thecooling water 55 in the mixing element inlet piping section 128 iscooler than the cooling water 55 exiting the filtration subsystem 102.

In one example embodiment of the temperature control subsystem 104,twenty-five percent of the cooling water 55 exiting the filtrationsubsystem 102 via the filter outlet piping section 121 enters themechanical cooler 137 via the mechanical cooling inlet piping section122. In this example embodiment, the cooling water 55 is cooled twentydegrees Fahrenheit in the mechanical cooler 137. The cooling water 55then exits the mechanical cooler 137 via the mechanical cooling outletpiping section 123. The cooling water 55 exiting the mechanical cooler137 via the mechanical cooling outlet piping section 123 mixes with thecooling water 55 that exited the filtration subsystem 102 via the filteroutlet piping section 121 and entered the mixing element inlet pipingsection 128. When this mixing occurs, the cooling water 55 entering themixing element inlet piping section 128 is cooled five degreesFahrenheit.

If a ten degree Fahrenheit cooling was needed, fifty percent of thecooling water 55 can be directed into the mechanical cooler 137 to becooled by twenty degrees. Thus, when the fifty percent portion is mixedwith the cooling water 55 that was not mechanically cooled, the overalltemperature drop of the cooling water 55 would be ten degrees.

FIG. 2 illustrates another example of a mechanical cooler. Inparticular, FIG. 2 illustrates a temperature control subsystem 104 thatincludes a multi-element mechanical cooler 221 consisting of a condenser223 and a chiller 222. In the embodiment illustrated in FIG. 2, thecondenser 223 is connected to the filter outlet piping section 121 via acondenser cooling inlet piping section 126. The condenser 223 isconnected to system return piping section 135 via a condenser coolingoutlet piping section 127.

In the embodiment illustrated in FIG. 2, a portion of the cooling water55 exiting the filtration subsystem 102 enters the condenser 223 via thecondenser cooling inlet piping section 126. The condenser 223 utilizesthe cooling water 55 as the cooling medium for the chiller 222. Thecooling water 55 utilized in the condenser 223 as a cooling medium exitsthe condenser 223 via the condenser cooling outlet piping section 127and is routed to the system return piping section 135. Thus, theconfiguration illustrated in FIG. 2 utilizes the cooling capacity of thecooling tower 100 to a maximum extent as well as prevents the heatabsorbed in the condenser 223 from being introduced into the open-loopcooling system 50.

In some atmospheric conditions, it may be the case that the coolingtower 100 cooled the cooling water 55 to a temperature below the desiredtemperature of the cooling cycle. Under these conditions, the coolingwater 55 needs to be heated to provide the required cooling of the datacenter air 145 through the air-handler units 105 (discussed furtherbelow). Thus, in one example embodiment, the temperature controlsubsystem 104 can include a mixing element 138 to increase thetemperature of the cooling water 55 if the cooling water 55 is too cold,as illustrated in FIG. 1.

In one example embodiment, the mixing element 138 is a valve that mixescooling water 55 with a high temperature exiting the air-handler units105 with the cooling water 55 with a low temperature in the temperaturecontrol subsystem 104. For example, FIG. 2 illustrates a mixing element138 that is a three-way bypass valve 220. In alternate embodiments, themixing element 138 may be an injection pump. The mixing element 138 canbe communicably connected to a control center that automaticallycontrols the mixing element 138 based on the temperature of the coolingwater 55 entering the temperature control subsystem 104.

As shown in FIG. 1, the mixing element 138 is connected to themechanical cooler 137 and the filtration subsystem 102 via the mixingelement inlet piping section 128 which is connected to the filter outletpiping section 121 and the mechanical cooling outlet piping section 123.As further illustrated in FIG. 1, the mixing element 138 is connected tothe system return piping section 135 via the mixing element cross-overpiping section 130. As further illustrated in FIG. 1, the mixing element138 is connected to the system pump inlet piping section 131 via themixing element outlet piping 129.

Furthermore, FIG. 1 illustrates that the mixing element 138 mixes thecooling water 55 entering the mixing element 138 via the mixing elementinlet piping section 128 with the cooling water 55 in the system returnpiping section 135 via the mixing element cross-over piping 130 thenroutes the cooling water 55 that has been mixed to the mixing elementoutlet piping section 129. By mixing the cooling water 55 entering themixing element 138 via the mixing element inlet piping section 128 withthe cooling water 55 entering the mixing element 138 via the mixingelement cross-over piping section 130 from the in the system returnpiping section 135, the mixing element 138 increases the temperature ofthe cooling water 55 exiting the mixing element 138 into the mixingelement outlet piping section 129.

In addition, in the example embodiment illustrated in FIG. 1, thequantity of cooling water 55 entering the mixing element 138 via themixing element cross-over piping section 130 from the system returnpiping section 135 may be determined by the wet bulb temperature of thedata center air 145. In alternate embodiments, the quantity of coolingwater 55 entering the mixing element 138 is determined by other physicalproperties of the open-loop cooling system 50. For example, the quantityof the cooling water 55 entering the mixing element 138 via the mixingelement cross-over piping section 130 from the system return pipingsection 135 is determined such that condensation does not form in theone or more air-handler units 105.

In addition, in an embodiment of the invention, the temperature controlsubsystem 104 may use a dedicated condenser pump and a dedicated chillerpump. For example, in the embodiment illustrated in FIG. 2, thetemperature control subsystem 104 includes a dedicated condenser pump212 and a dedicated chiller pump 211.

In this embodiment, an alternative piping configuration can be utilized.For example, as illustrated in FIG. 2, the condenser cooling inletpiping section 126 is connected to the filter outlet piping section 121.The mechanical cooling inlet piping section 122 is connected to themixing element outlet piping section 129 rather than the filter outletpiping section 121 as illustrated in FIG. 1. Additionally, in thisembodiment, cooling water 55 exiting the chiller 222 circulates into thesystem pump inlet piping section 131 rather than into the mixing elementinlet piping section 128 as illustrated in FIG. 1. In alternateembodiments, the piping configuration between the temperature controlsubsystem 104 and the open-loop cooling system 50 may take otherconfigurations.

In the embodiment illustrated in FIG. 2, the dedicated condenser pump212 circulates cooling water 55 through the condenser 223 via thecondenser cooling inlet piping section 126. The dedicated condenser pump212 then circulates the cooling water 55 out of the condenser 223 intothe system return piping section 135 via the condenser cooling outletpiping section 127.

As further illustrated in FIG. 2, the dedicated chiller pump 211circulates cooling water 55 into the chiller 222 via the mechanicalcooling inlet piping section 122. The dedicated chiller pump 211 thencirculates the cooling water 55 out of the chiller 222 into the systempump inlet piping section 131 via the mechanical cooling outlet pipingsection 123. In alternate embodiments, the open-loop cooling system 50may utilize configurations without a dedicated condenser pump and/or adedicated chiller pump.

As discussed above, the cooling tower 100 is in series with thetemperature control subsystem 104. This allows the cooling tower 100 andthe temperature control subsystem 104 to cool the cooling water 55 towithin a zone of efficient cooling. For example, FIG. 3 illustrates azone of efficient cooling 301 for the example embodiment illustrated inFIG. 1 at average atmospheric conditions at approximately 4200 feetabove sea level. In alternate embodiments, the zone of efficient coolingwould shift due to atmospheric conditions.

The open-loop cooling system 50 would be most efficient below a givenatmospheric wet bulb temperature. For example, the open-loop coolingsystem 50 illustrated in FIG. 1 may be most efficient in areas of theworld with a maximum atmospheric wet bulb temperature of 70 degreesFahrenheit. FIG. 3 illustrates the psychometric properties below themaximum wet bulb temperature of 70 degrees Fahrenheit 302. This physicalcondition produces the highest efficiencies in the cooling tower 100. Inalternate embodiments, the maximum atmospheric wet bulb temperatureproducing the highest efficiencies may vary with the particular systemconfiguration, ambient atmospheric conditions, and elevation.

As the cooling water 55 circulates through the open-loop cooling system50 the cooling water 55 is subject to psychometric changes. Apsychometric change of cooling water 55 in a cooling tower 100 includesan initial physical state, a final physical state, and a change lineillustrating the intermediate physical states between the initial andfinal physical state. For example, FIG. 3 illustrates a cooling towerpsychometric change 303 of the cooling water 55 in the cooling tower100. The cooling tower psychometric change 303, for example, includes aninitial physical state 304, a final physical state 305, and a changeline 306.

The cooling tower psychometric change 303 represents the psychometricchanges of the cooling water 55 as the cooling water 55 circulates fromthe system return piping section 135 through the cooling tower 100 andinto the cooling tower outlet piping section 116. The initial physicalstate 304 represents the physical properties of the cooling water 55 inthe system return piping section 135. The final physical state 305represents the physical properties of the cooling water 55 in thecooling tower outlet piping section 116. The change line 306 representsthe cooling occurring in the cooling tower 100 due to the mixing of thecooling water 55 with the atmospheric air 51 with a low wet bulbtemperature. In alternate embodiments, the cooling tower psychometricchange 303 will vary with physical properties of the system and theambient conditions of the atmospheric air 51.

As illustrated in FIG. 3, the final physical state 305 is located in thezone of efficient cooling 301. This illustrates that in the embodimentillustrated in FIG. 1 during the cooling tower psychometric change 303the cooling tower 100 normally has the ability of to provide sufficientcooling to the cooling water 55 for circulation in the open-loop coolingsystem 50.

Alternatively, if adverse ambient conditions exist such as atmosphericair 51 with a high wet bulb temperature, the cooling tower 100 mayproduce a cooling tower psychometric change in which the final physicalstate of the cooling water 55 is outside the zone of efficient cooling301. For example, FIG. 3 illustrates an inadequate cooling towerpsychometric change 303 a. The inadequate cooling tower psychometricchange 303 a includes the initial physical state 304, an intermediatephysical state 305 a, and an intermediate change line 306 a.

The inadequate cooling tower psychometric change 303 a represents thepsychometric changes of the cooling water 55 as the cooling water 55circulates from the system return piping section 135 through the coolingtower 100 and into the cooling tower outlet piping section 116. Theinitial physical state 304 represents the physical properties of thecooling water 55 in the system return piping section 135. Theintermediate physical state 305 a represents the physical properties ofthe cooling water 55 in the cooling tower outlet piping section 116. Theintermediate change line 306 a represents the cooling occurring in thecooling tower 100 due to the mixing of the cooling water 55 andatmospheric air 51 with a higher-than-optimal wet bulb temperature. Inalternate embodiments, the inadequate cooling tower psychometric change303 a will vary with physical properties of the system and the ambientconditions of the atmospheric air 51.

As illustrated in FIG. 3, the intermediate physical state 305 a islocated outside of the zone of efficient cooling 301. This illustratesthat in the embodiment illustrated in FIG. 1 during the inadequatecooling tower psychometric change 303 a when adverse atmosphericconditions exist, the cooling tower 100 may be unable to providesufficient cooling to the cooling water 55 for circulation in theopen-loop cooling system 50.

In this situation, additional cooling may be necessary. For example,FIG. 3 illustrates a mechanical cooler psychometric change 307 of thecooling water 55 in the mechanical cooler 137. In this situation, theopen-loop cooling system 50 embodied in FIG. 1 introduces the coolingwater 55 into a mechanical cooler 137. Within the mechanical cooler 137,the cooling water 55 undergoes psychometric changes. For example, FIG. 3illustrates a mechanical cooler psychometric change 307 of the coolingwater 55 in the mechanical cooler 137.

As with the cooling tower psychometric change 303, the mechanical coolerpsychometric change 307 can include an initial psychometric state, afinal psychometric state, and a trend line illustrating the intermediatepsychometric states between the initial and final psychometric states.For example, in FIG. 3, the mechanical cooling psychometric change 307includes an initial psychometric state 308 (which may coincide withintermediate physical state 305 a), a final psychometric state 310, anda trend line 309.

The mechanical cooler psychometric change 307 represents thepsychometric changes of the cooling water 55 as the cooling water 55circulates from the filter outlet piping section 121 through themechanical cooler 137 and into the mixing element inlet piping section128. The initial psychometric state 308 represents the physicalproperties of the cooling water 55 in the filter outlet piping section121. The final psychometric state 310 represents the physical propertiesof the cooling water 55 in the mixing element inlet piping section 128.The trend line 309 represents the cooling occurring due to themechanical cooler 137. In alternate embodiments, the mechanical coolerpsychometric change 307 will vary with physical properties of themechanical cooler 137 and the system configuration.

As illustrated in FIG. 3, the final psychometric state 310 is locatedwithin the zone of efficient cooling 301. Thus, the cooling water 55mechanically has been cooled from a physical state outside the zone ofefficient cooling 301, such as the intermediate physical state 305 athat resulted from the inadequate cooling tower psychometric change 303a, to be within the zone of efficient cooling 301. This illustrates thatduring the mechanical cooling psychometric change 307 the mechanicalcooler 137 has the ability to provide supplemental mechanical cooling tothe cooling water 55 for circulation in the open-loop cooling system 50.

Returning to FIG. 1, the remaining components of the open-loop coolingsystem 50 will be described. As shown in FIG. 1, the mixing element 138is connected to the one or more system pumps 106 via the mixing elementoutlet piping section 129 and the system pump inlet piping section 131.In the example embodiment illustrated in FIG. 1, after the cooling water55 exits the mixing element 138 via the mixing element outlet pipingsection 129, the one or more system pumps 106 pump the cooling water 55in through the system pump inlet piping section 131, out through thesystem pump outlet piping section 132, and into the air-handler inletpiping section 133. In alternate embodiments, the particularconfiguration of these components may vary.

In addition to the system pumps 106 pumping the cooling water exitingthe mixing element 138, the system pumps 106 can have variousconfigurations. For example, in the embodiment illustrated in FIG. 2,the system pumps 106 a and 106 b are configured in parallel. In thisconfiguration, one of system pumps is designated as the operating systempump 106 a, and the other system pump is designated as the standbysystem pump 106 b. That is, the operating system pump 106 a pumps thecooling water 55 while the standby system pump 106 b remains in standby.In alternate embodiments, the system pumps 106 may be configured inseries or a single pump may be utilized.

As shown in FIG. 1, the one or more system pumps 106 are connected tothe one or more air-handler units 105 via the system pump outlet pipingsection 132 and the air-handler inlet piping section 133. As furthershown in FIG. 1, the air-handler units 105 are connected to the coolingtower 100 via the system return piping section 135.

Generally, the air-handler units 105 provide an interface between thecooling water 55 cooled by the open-loop cooling system 50 and datacenter air 145 that has been heated in the computer data center 140. Forexample, FIG. 1 illustrates that the data center air 145 is moved intothe air-handler units 105 though ducting. Specifically, FIG. 1illustrates the air-handler units 105 connected to the computer datacenter 140 via inlet ducting 141 and outlet ducting 142.

Because the cooling water 55 entering the air-handler units 105 via theair-handler inlet piping section 133, is cooler than the data center air145 entering the air-handler units 105 via the inlet ducting 141, theheat in the data center air 145 transfers to the cooling water 55, thuscooling the data center air 145. The data center air 145 having beencooled, returns to the computer data center 140 via the outlet ducting142, while the cooling water 55 which has been heated enters the systemreturn piping section 135 to be directed to the cooling tower 100 tobegin the cooling cycle as described above.

In one example embodiment of the air-handler units 105, the air-handlerunits 105 contain a cooling coil 401. For example, FIG. 4 illustrates anair-handler unit 105 containing a cooling coil 401. In the embodimentillustrated in FIG. 4, the air-handler inlet piping section 133 connectsto the cooling coil 401. The system pumps 106 pump the cooling water 55into the cooling coil 401 via the air-handler inlet piping section 133.The cooling water 55 circulates through the cooling coil 401 then exitsthe cooling coil 401 into the system return piping section 135.

In the example embodiment of the air-handler unit 105 illustrated inFIG. 4, the data center air 145 enters the air-handler unit 105 via theinlet ducting 141 then moves across the cooling coil 401. As the datacenter air 145 moves across the cooling coil 401, the data center air145 transfers heat to the cooling water 55 moving through the coolingcoil 401. The data center air 145 exits the air-handler unit 105 throughthe outlet ducting 142.

As shown in FIG. 1, the inlet ducting 141 may contain a humidificationelement 143. In the embodiment illustrated in FIG. 1, the humidity ofthe data center air 145 may be controlled by the humidification element143. For example, if the humidity level needs to be increased tomaintain the correct data center environment, the humidification element143 may inject water into the inlet ducting 141 as the data center air145 enters the air-handler units 105. In alternate embodiments, thehumidity of the data center air 145 could be controlled through use ofan evaporative media section, or directly in the data center 140.

In an example embodiment of the open-loop cooling system 50, an airremoval subsystem 500 may be included to remove atmospheric air 51 fromthe cooling water 55. For example, FIG. 5 illustrates an example of anair removal subsystem 500 that may be included in an embodiment of theopen loop cooling system 50 to remove atmospheric air 51 from thecooling water 55. In the embodiment illustrated in FIG. 5, the airremoval subsystem 500 includes a supply piping port 502, a vent pipingsection 504, and a return piping port 505.

As shown in FIG. 5, the supply piping port 502 is provided on the top ofthe air-handler inlet piping section 133. The return piping port 505 isprovided on the top of the system return piping section 135. The supplypiping port 502 is connected via the vent piping section 504 to thereturn piping port 505. In alternate embodiments, the supply piping port502 may be located on a different section or multiple piping sections ofthe open-loop cooling system 50.

In addition, in the embodiment illustrated in FIG. 5, the air removalsubsystem 500 may function due to a differential pressure between theair-handler inlet piping section 133 and the system return pipingsection 135. The differential pressure forces atmospheric air 51 in theair-handler inlet piping section 133 through the supply piping port 502,through vent piping section 504, and through the return piping port 505.The atmospheric air 51 is mixed with the cooling water 55 in the systemreturn piping section 135 and is directed back to the cooling tower 100.The air removal subsystem 500 illustrated in FIG. 5 can be located at ahigh point of the open-loop cooling system 50. In alternate embodiments,multiple air removal subsystems 500 may be located throughout thesystem.

In an example embodiment of the open-loop cooling system 50, airprevention subsystems 510 and 510 a may be included to prevent air fromentering the air-handler units 105. For example, FIG. 5 illustratesexamples of air prevention subsystems 510 and 510 a that may be includedin an embodiment of the open loop cooling system to prevent atmosphericair 51 remaining in the cooling water 55 from entering the air-handlerunits 105.

As illustrated in FIG. 5, the air prevention subsystems 510 and 510 ainclude the air-handler inlet piping section 133 connected to the systempump outlet piping section 132 at the bottom (illustrated in 510) or theside (illustrated in 510 a) of the piping and a vent valve 511. Inalternate embodiments, the specific piping sections utilized to preventair from entering the air-handler units 105 may vary.

As illustrated in FIG. 5, the cooling water 55 is allowed to exit thesystem pump outlet piping section 132 and enter the air-handler inletpiping section 133 without the atmospheric air 51 entering theair-handler inlet piping section 133. Therefore, the cooling water 55enters the air-handler units 105 without the atmospheric air 51. Theatmospheric air 51 is vented via the vent valve 511. In alternateembodiments, the air remaining may be disposed of through other meansknown in the art.

In an example embodiment illustrated in FIG. 2 of the open-loop coolingsystem 50, the system pumps 106 a and 106 b and the tower pumps 101 aand 101 b are configured in parallel (as discussed above, FIG. 2specifically illustrates examples of the operating tower pump 101 a andstandby tower pump 101 b along with the operating system pump 106 a andthe standby system pump 106 b configured in parallel) that may require afreeze protection subsystem 600 to prevent damage if the parallel pumpsare exposed to temperatures below thirty-two degrees Fahrenheit. Forexample, FIG. 6 illustrates an embodiment of a freeze protectionsubsystem 600. The freeze protection subsystem 600 includes a standbypump 602, a standby pump check valve 603, a freeze protection cross-overpiping section 606, a standby pump outlet piping section 607, anoperating pump 601, an operating pump outlet piping section 605, and atemperature sensor 604.

The freeze protection subsystem 600 operates by forming a hole in thedisc of the standby pump check valve 603. This hole allows a smallamount of the cooling water 55 pumped by the operating pump 601 to flowfrom the operating pump outlet piping section 605, through the freezeprotection cross-over piping section 606, down the standby pump outletpiping section 607, through the hole drilled in the disc of the standbypump check valve 603, and into the standby pump 602.

In addition, the freeze protection subsystem 600 may include atemperature sensor 604. The temperature sensor 604 measures thetemperature of the cooling water 55 backflowing through the standby pump602. If the temperature of the cooling water 55 backflowing through thestandby pump 602 is below a preset temperature, the standby pump 602becomes the operating pump 601 and the operating pump 601 becomes thestandby pump 602.

The present invention can be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. Thus, thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

1. An open-loop cooling system that provides cooling water for use incooling environmentally sensitive volumes of air, the open-loop coolingsystem comprising: an evaporative heat exchanger that mixes coolingwater with air having a low wet bulb temperature to cool the coolingwater; a temperature control subsystem, connected to the evaporativeheat exchanger, that controls the temperature of the cooling watercirculating in the open-loop cooling system, the temperature controlsubsystem comprising: a temperature monitor that measures thetemperature of the cooling water exiting the evaporative heat exchanger;and a mechanical cooler that provides supplementary mechanical coolingto the cooling water if the temperature monitor indicates thetemperature of the cooling water is higher than a desired coolingtemperature; and at least one air-handler unit that facilitates thetransfer of heat from the environmentally sensitive volume of air to thecooling water.
 2. The open-loop cooling system recited in claim 1,wherein the environmentally sensitive volume is a data center.
 3. Theopen-loop cooling system recited in claim 1, wherein the evaporativeheat exchanger is a cooling tower.
 4. The open-loop cooling systemrecited in claim 1, wherein the mechanical cooler comprises: a chiller,that provides the supplementary mechanical cooling to the cooling water;and a condenser, wherein the condenser is configured to use coolingwater exiting the evaporative heat exchanger as inlet water to cool themechanical cooler condenser, thereby utilizing the cooling occurring inthe evaporative heat exchanger.
 5. The open-loop cooling system recitedin claim 1, wherein the desired cooling temperature of the cooling wateris determined by the wet bulb temperature of air in the data center. 6.The open-loop cooling system recited in claim 1, further comprising achemical treatment and monitoring subsystem.
 7. The open-loop coolingsystem recited in claim 3, wherein the air utilized in the cooling toweris atmospheric air with a low wet bulb temperature.
 8. The open-loopcooling system recited in claim 7, wherein following the cooling of thecooling water, the atmospheric air is exhausted to an ambientatmosphere, thereby using the ambient atmosphere as a heat sink of theopen-loop cooling system.
 9. The open-loop cooling system recited inclaim 1, further comprising a mixing element that heats the coolingwater if the temperature control subsystem indicates the temperature ofthe cooling water is cooler than the desired cooling temperature. 10.The open-loop cooling system recited in claim 9, wherein the mixingelement is a three-way valve that mixes warmer cooling water returningfrom the air-handler with cooler cooling water from the cooling tower.11. The open-loop cooling system recited in claim 1, further comprisingan air removal subsystem having a piping configuration, wherein theair-handler supply piping stems from a bottom or a side of a system pumpoutlet piping section, such that air is not directed to the air-handlerunit.
 12. An open-loop cooling system for use in cooling a data center,comprising: at least one air-handler unit configured to facilitate thetransfer of heat from air in the data center to cooling water thatcirculates through a cooling water system, the cooling water systemcomprising: a cooling tower connected to the air-handler unit, whereinthe cooling tower allows cooling water to mix with air having a low wetbulb temperature; and a temperature control subsystem, connected to thecooling tower and the air-handler unit, that controls the temperature ofthe cooling water circulating in the cooling water system, thetemperature control subsystem comprising: a temperature monitor thatmeasures the temperature of the cooling water exiting the cooling tower;a mechanical cooler that provides supplementary mechanical cooling tothe cooling water if the temperature control subsystem indicates thetemperature of the cooling water is higher than the desired coolingtemperature; and a mixing element that heats the cooling water if thetemperature control subsystem indicates the temperature of the coolingwater is cooler than the desired cooling temperature.
 13. The open-loopcooling system recited in claim 11, wherein the desired coolingtemperature of the cooling water is determined by the wet bulbtemperature of air in the data center.
 14. The open-loop cooling systemrecited in claim 11, further comprising a chemical treatment andmonitoring subsystem.
 15. The open-loop cooling system recited in claim11, wherein the air utilized in the cooling tower is atmospheric airwith a low wet bulb temperature.
 16. The open-loop cooling systemrecited in claim 12, wherein following the cooling of the cooling water,the atmospheric air is exhausted to an ambient atmosphere, thereby usingthe ambient atmosphere as a heat sink of the open-loop cooling system.17. A method for data center cooling using an open-loop evaporativesystem that facilitates the production of cooling water at a desiredcooling temperature, the method comprising: mixing heated cooling waterwith air having a low wet bulb temperature in a cooling tower, therebyutilizing the latent heat of vaporization to cool the cooling water;circulating at least a portion of the cooling water through atemperature control subsystem, wherein the temperature control subsystemmeasures the temperature of the cooling water; comparing the temperaturemeasured in the temperature control subsystem to the desired coolingwater temperature; altering the temperature of the cooling water in thetemperature control subsystem if the cooling water temperature isdifferent from the desired cooling temperature; circulating the coolingwater through one or more cooling coils of an air-handler unit, whereinair from the data center is forced across the cooling coil such that theair from the data center transfers its heat to the cooling water; andreturning the heated cooling water to the cooling tower.
 18. The methodas recited in claim 17, further comprising determining the desiredtemperature from the wet bulb temperature of air in the data center. 19.The method as recited in claim 16, further comprising: utilizingatmospheric air having a low wet bulb temperature in the cooling tower;and exhausting the atmospheric air after cooling the cooling wateroccurs back to the ambient atmosphere.
 20. The method as recited inclaim 19, further comprising monitoring the chemical composition of thecooling water.